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محتويات الكتابContents
Acknowledgements viii
Preface ix
List of acronyms xi
Introduction 1
Organic matter decomposition and the soil food web 5
Soil organic matter 5
The soil food web 5
Decomposition process 7
Non-humic substances: significance and function 8
Compounds and function of humus 8
Natural factors influencing the amount of organic matter 11
Temperature 11
Soil moisture and water saturation 12
Soil texture 12
Topography 13
Salinity and acidity 13
Vegetation and biomass production 13
Practices that influence the amount of organic matter 15
Human interventions that influence soil organic matter 15
Practices that decrease soil organic matter 15
Decrease in biomass production 15
Replacement of perennial vegetation 15
Replacement of mixed vegetation with monoculture of crops and
pastures 16
High harvest index 16
Use of bare fallow 17
Decrease in organic matter supply 17
Burning of natural vegetation and crop residues 17
Overgrazing 17
Removal of crop residues 17
Increased decomposition rates 18
Tillage practices 18
Drainage 19
Fertilizer and pesticide use 19
Practices that increase soil organic matter Increased biomass production 20
Increased water availability for plants: water harvesting and irrigation 20
Balanced fertilization 21
Cover crops 21
Improved vegetative stands 22
iv
Agroforestry and alley cropping 23
Reforestation and afforestation 26
Regeneration of natural vegetation 27
Increased organic matter supply 27
Protection from fire 27
Crop residue management 27
Utilizing forage by grazing rather than by harvesting 28
Integrated pest management 28
Applying animal manure or other carbon-rich wastes 28
Compost 29
Mulch or permanent soil cover 29
Decreased decomposition rates 30
Reduced or zero tillage 30
Creating drought-resistant soil 35
Effect of soil organic matter on soil properties 35
Inefficient use of rainwater 35
Increased soil moisture 35
Reduced soil erosion and improved water quality 38
Key factors in sustained food production 41
Increased plant productivity 41
Increased fertilizer efficiency 41
Reduced waterlogging 42
Increased yields 42
Reduced herbicide and pesticide use 44
Increased biodiversity 45
Resilience 46
The role of conservation agriculture in organic matter
deposition and carbon sequestration 47
Principles of conservation agriculture 47
Organic matter deposition 47
Increased carbon sequestration 48
Conclusions 51
Bibliography 53
Annexes
Soil organisms 61
Effects of organic matter on soil properties
مواضيع مشابهة:
اهميه المادة العضويه للمتخصصين
اقتباس